1. Field of the Invention
Generally, this invention relates to downhole tools for use in a well. In particular, but not by way of limitation, this invention relates to those tools utilizing a bypass to allow well fluids located below the tool to bypass the main fluid passages of the tool as the tool string is being stung into, or out of, a production packer.
2. Description of Prior Art
During the course of drilling an oil or gas well, one operation which is often performed is to lower a testing string into the well to test the production capabilities of the hydrocarbon producing underground formations intersected by the well. This testing is accomplished by lowering a string of pipe, commonly referred to as the drill pipe, into the well with a formation tester valve attached. Another tool typically run into the well is known as a Tubing String Testing Valve (TST), which is a full opening test valve that allows the drill stem test string to be pressure tested while running in the hole. The TST contains a flapper type valve which acts somewhat similar to a check valve. As the tool string is being run into the hole, the test string annulus can fill with fluid. However, if pressure is placed on the tubing string, the TST flapper valve will seat and seal, thereby allowing the string to be pressure tested. The pressure testing of the drill string can be accomplished as many times as desired.
Once the test string is run to its desired depth, it is then necessary to sting, via a set of seals located on the bottom of the test string, into the production packer. However, if it is necessary to pull the test string up, the TST flapper valve will act as a check valve, thereby causing a pressure decrease due to a increase in volume in the annulus below the TST flapper valve. This decrease in pressure can operate to affect the seals on the bottom of the test string, as well as the seals on the production packer itself.
Furthermore, if one of the other tester valves located in the test string have been closed for testing reasons, the pulling in and out of the seals can act to destroy the seal integrity on the stinger of the test string as well as effecting the seals in the production packer, by causing a piston effect due to the closed annulus area.
Several types of bypasses have been employed with use in drill stem testing. U.S. Pat. No. 2,740,479 to Schwegman provided a bypass which allowed fluid from below the formation tester to flow upward through the packer mandrel and through the lower end of the tester valve, then outward through a bypass port so that it could flow upward in the annulus between the tester valve and the wellbore in order to bypass the piston effect of the larger packer located below the tester valve.
Another example of such a bypass is seen in U.S. Pat. No. 4,582,140 to Barrington, assigned to Halliburton, assignee of the present invention. The Barrington device allowed a choice of several possible functions of that bypass tool In a first arrangement, a bypass is run into the wellbore in an open position and is then latched closed upon operation of the tool by setting down weight. In the second arrangement, the open bypass is run into the well, the bypass is closed by setting down weight; however, the bypass could reopen when the weight was picked up. Finally, the Barrington invention allowed the bypass port to be completely eliminated when it was desired to run the tool without bypass.
However, the bypass valves of the prior art do not deal with the bypass in which a TST valve has been utilized. Therefore, in reference to the present invention, there are several features not possible with the prior art bypass valves. One feature includes the fact that a rupture disk is utilized, said rupture disk being operable by transmitting pressure via an oil chamber to rupture the disk. Also, as an added feature there is included two sets of shear pins provided in the tool. One set of shear pins allows the activation of the time delay function of the present invention; the second set allows for the floating piston to begin its travel, and move the operating mandrel after a predetermined amount of oil has been metered out of the second oil chamber.
Another feature of the present invention utilizes a metering cartridge in order to implement its time delay. The metering cartridge utilizes a restriction, and the restriction size can be varied, hence directly effecting the amount of time necessary to meter the oil.
Also there is contained a recess neck on the operating mandrel, thereby effectively allowing the metering cartridge to be bypassed. When the recess neck of the operating mandrel reaches the metering cartridge, the flow of oil can bypass the metering cartridge, and allow rapid movement of the operating mandrel to import a jarring effect in the tool. Once this jarring effect is accomplished, the ported mandrel will effectively seal off the bypass ports. Furthermore, another feature of the invention is that once the bypass ports have been closed, hydrostatic pressure from within the tubing string will keep the ported mandrel in a closed position alleviating the need for a locking mechanism.
Another feature of the invention allows for pressure testing the seal of the ported mandrel before the test tool is run into the hole. Yet another feature includes having the oil in the second chamber as well as air in a separate chamber under atmospheric pressure, thereby allowing a differential pressure which the floating pistons can act against.